A LOT of Democrats are suddenly sounding very sorry they attacked President Bush on what he knew about 9/11 before it happened – and the polls show why.

Less than two weeks after Democrats from Sen. Hillary Clinton to House Democratic Leader Dick Gephardt went after Bush, it seems clear the president has won this round.

Bush’s job-approval rating is still up in the stratosphere – 74 percent in a new Harris Poll – and terrorism again tops the national agenda (the top concern for 30 percent of Americans vs. 17 percent for the economy).

“In the short term, it backfired – the Democrats probably helped boost Bush’s numbers by pushing the agenda back to terrorism, which is his strength, instead of issues like Social Security,” says GOP pollster John McLaughlin.

“There’s a window in May-June when people can focus on politics before summer – and now the Democrats have blown the chance to have that time focus on their domestic agenda.”

Democratic strategists privately say their party’s leaders showed their frustration at the president’s popularity when they jumped on the revelation that Bush got a vague warning about al Qaeda and hijackings last August.

Worst of all, they say, was House Democratic leader (and wannabe presidential contender) Dick Gephardt’s use of Watergate rhetoric about “what the president, what the White House knew . . . [and] when they knew it.”

“The public doesn’t want to go on a witch hunt over this. They like the job Bush is doing and don’t want to change their view of him. It was silly to try to personalize this against him,” says a Democratic strategist.

“It’s like FDR and Pearl Harbor – people didn’t blame him for the Japanese attack. They judged him, as they judge Bush or any president, by what he did afterward.”

The Dems are so frustrated by Bush’s popularity that they seem to have forgotten the lesson that they, above all, should have learned from Bill Clinton’s success at surviving GOP attacks over Sexgate, says GOP strategist Rich Galen.

“Treating the president badly, and, in the public’s mind, unfairly doesn’t work. But I’m thrilled they’re doing it – every day that goes by when they try is another day when they can’t get traction on Medicare,” he said.

In fact, Dem pollster Mark Mellman claims the proof that Democrats are acting on principle in asking “what did Bush know” is precisely that it’s dumb politics for them for this fall’s congressional election.

“From a political point of view, does it make sense to fight an election about terrorism? No,” Mellman says. “It’s not politics.”